I just got this idea from nowhere - A OCR (Optical Character Recognition) web service. I did a search to find out that one such web service already exists. It would be a very good web service demo is one is giving a session on Web Services. Though the focus of a good web service demo should be on the interoperability aspect of it, the OCR demo would be cool. Channel 9 has a video which shows an interop between a legacy application on the CISC and a desktop Avalon application. Check it out.